1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
4 */
5
6 #include <linux/dcache.h>
7 #include <linux/fs.h>
8 #include <linux/gfp.h>
9 #include <linux/init.h>
10 #include <linux/module.h>
11 #include <linux/mount.h>
12 #include <linux/srcu.h>
13
14 #include <linux/fsnotify_backend.h>
15 #include "fsnotify.h"
16
17 /*
18 * Clear all of the marks on an inode when it is being evicted from core
19 */
__fsnotify_inode_delete(struct inode * inode)20 void __fsnotify_inode_delete(struct inode *inode)
21 {
22 fsnotify_clear_marks_by_inode(inode);
23 }
24 EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
25
__fsnotify_vfsmount_delete(struct vfsmount * mnt)26 void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
27 {
28 fsnotify_clear_marks_by_mount(mnt);
29 }
30
31 /**
32 * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
33 * @sb: superblock being unmounted.
34 *
35 * Called during unmount with no locks held, so needs to be safe against
36 * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
37 */
fsnotify_unmount_inodes(struct super_block * sb)38 static void fsnotify_unmount_inodes(struct super_block *sb)
39 {
40 struct inode *inode, *iput_inode = NULL;
41
42 spin_lock(&sb->s_inode_list_lock);
43 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
44 /*
45 * We cannot __iget() an inode in state I_FREEING,
46 * I_WILL_FREE, or I_NEW which is fine because by that point
47 * the inode cannot have any associated watches.
48 */
49 spin_lock(&inode->i_lock);
50 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
51 spin_unlock(&inode->i_lock);
52 continue;
53 }
54
55 /*
56 * If i_count is zero, the inode cannot have any watches and
57 * doing an __iget/iput with SB_ACTIVE clear would actually
58 * evict all inodes with zero i_count from icache which is
59 * unnecessarily violent and may in fact be illegal to do.
60 * However, we should have been called /after/ evict_inodes
61 * removed all zero refcount inodes, in any case. Test to
62 * be sure.
63 */
64 if (!atomic_read(&inode->i_count)) {
65 spin_unlock(&inode->i_lock);
66 continue;
67 }
68
69 __iget(inode);
70 spin_unlock(&inode->i_lock);
71 spin_unlock(&sb->s_inode_list_lock);
72
73 if (iput_inode)
74 iput(iput_inode);
75
76 /* for each watch, send FS_UNMOUNT and then remove it */
77 fsnotify_inode(inode, FS_UNMOUNT);
78
79 fsnotify_inode_delete(inode);
80
81 iput_inode = inode;
82
83 cond_resched();
84 spin_lock(&sb->s_inode_list_lock);
85 }
86 spin_unlock(&sb->s_inode_list_lock);
87
88 if (iput_inode)
89 iput(iput_inode);
90 /* Wait for outstanding inode references from connectors */
91 wait_var_event(&sb->s_fsnotify_inode_refs,
92 !atomic_long_read(&sb->s_fsnotify_inode_refs));
93 }
94
fsnotify_sb_delete(struct super_block * sb)95 void fsnotify_sb_delete(struct super_block *sb)
96 {
97 fsnotify_unmount_inodes(sb);
98 fsnotify_clear_marks_by_sb(sb);
99 }
100
101 /*
102 * Given an inode, first check if we care what happens to our children. Inotify
103 * and dnotify both tell their parents about events. If we care about any event
104 * on a child we run all of our children and set a dentry flag saying that the
105 * parent cares. Thus when an event happens on a child it can quickly tell if
106 * if there is a need to find a parent and send the event to the parent.
107 */
__fsnotify_update_child_dentry_flags(struct inode * inode)108 void __fsnotify_update_child_dentry_flags(struct inode *inode)
109 {
110 struct dentry *alias;
111 int watched;
112
113 if (!S_ISDIR(inode->i_mode))
114 return;
115
116 /* determine if the children should tell inode about their events */
117 watched = fsnotify_inode_watches_children(inode);
118
119 spin_lock(&inode->i_lock);
120 /* run all of the dentries associated with this inode. Since this is a
121 * directory, there damn well better only be one item on this list */
122 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
123 struct dentry *child;
124
125 /* run all of the children of the original inode and fix their
126 * d_flags to indicate parental interest (their parent is the
127 * original inode) */
128 spin_lock(&alias->d_lock);
129 list_for_each_entry(child, &alias->d_subdirs, d_child) {
130 if (!child->d_inode)
131 continue;
132
133 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
134 if (watched)
135 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
136 else
137 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
138 spin_unlock(&child->d_lock);
139 }
140 spin_unlock(&alias->d_lock);
141 }
142 spin_unlock(&inode->i_lock);
143 }
144
145 /* Are inode/sb/mount interested in parent and name info with this event? */
fsnotify_event_needs_parent(struct inode * inode,struct mount * mnt,__u32 mask)146 static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt,
147 __u32 mask)
148 {
149 __u32 marks_mask = 0;
150
151 /* We only send parent/name to inode/sb/mount for events on non-dir */
152 if (mask & FS_ISDIR)
153 return false;
154
155 /*
156 * All events that are possible on child can also may be reported with
157 * parent/name info to inode/sb/mount. Otherwise, a watching parent
158 * could result in events reported with unexpected name info to sb/mount.
159 */
160 BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT);
161
162 /* Did either inode/sb/mount subscribe for events with parent/name? */
163 marks_mask |= fsnotify_parent_needed_mask(inode->i_fsnotify_mask);
164 marks_mask |= fsnotify_parent_needed_mask(inode->i_sb->s_fsnotify_mask);
165 if (mnt)
166 marks_mask |= fsnotify_parent_needed_mask(mnt->mnt_fsnotify_mask);
167
168 /* Did they subscribe for this event with parent/name info? */
169 return mask & marks_mask;
170 }
171
172 /*
173 * Notify this dentry's parent about a child's events with child name info
174 * if parent is watching or if inode/sb/mount are interested in events with
175 * parent and name info.
176 *
177 * Notify only the child without name info if parent is not watching and
178 * inode/sb/mount are not interested in events with parent and name info.
179 */
__fsnotify_parent(struct dentry * dentry,__u32 mask,const void * data,int data_type)180 int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
181 int data_type)
182 {
183 const struct path *path = fsnotify_data_path(data, data_type);
184 struct mount *mnt = path ? real_mount(path->mnt) : NULL;
185 struct inode *inode = d_inode(dentry);
186 struct dentry *parent;
187 bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;
188 bool parent_needed, parent_interested;
189 __u32 p_mask;
190 struct inode *p_inode = NULL;
191 struct name_snapshot name;
192 struct qstr *file_name = NULL;
193 int ret = 0;
194
195 /*
196 * Do inode/sb/mount care about parent and name info on non-dir?
197 * Do they care about any event at all?
198 */
199 if (!inode->i_fsnotify_marks && !inode->i_sb->s_fsnotify_marks &&
200 (!mnt || !mnt->mnt_fsnotify_marks) && !parent_watched)
201 return 0;
202
203 parent = NULL;
204 parent_needed = fsnotify_event_needs_parent(inode, mnt, mask);
205 if (!parent_watched && !parent_needed)
206 goto notify;
207
208 /* Does parent inode care about events on children? */
209 parent = dget_parent(dentry);
210 p_inode = parent->d_inode;
211 p_mask = fsnotify_inode_watches_children(p_inode);
212 if (unlikely(parent_watched && !p_mask))
213 __fsnotify_update_child_dentry_flags(p_inode);
214
215 /*
216 * Include parent/name in notification either if some notification
217 * groups require parent info or the parent is interested in this event.
218 */
219 parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS;
220 if (parent_needed || parent_interested) {
221 /* When notifying parent, child should be passed as data */
222 WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type));
223
224 /* Notify both parent and child with child name info */
225 take_dentry_name_snapshot(&name, dentry);
226 file_name = &name.name;
227 if (parent_interested)
228 mask |= FS_EVENT_ON_CHILD;
229 }
230
231 notify:
232 ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0);
233
234 if (file_name)
235 release_dentry_name_snapshot(&name);
236 dput(parent);
237
238 return ret;
239 }
240 EXPORT_SYMBOL_GPL(__fsnotify_parent);
241
fsnotify_handle_inode_event(struct fsnotify_group * group,struct fsnotify_mark * inode_mark,u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * name,u32 cookie)242 static int fsnotify_handle_inode_event(struct fsnotify_group *group,
243 struct fsnotify_mark *inode_mark,
244 u32 mask, const void *data, int data_type,
245 struct inode *dir, const struct qstr *name,
246 u32 cookie)
247 {
248 const struct path *path = fsnotify_data_path(data, data_type);
249 struct inode *inode = fsnotify_data_inode(data, data_type);
250 const struct fsnotify_ops *ops = group->ops;
251
252 if (WARN_ON_ONCE(!ops->handle_inode_event))
253 return 0;
254
255 if ((inode_mark->mask & FS_EXCL_UNLINK) &&
256 path && d_unlinked(path->dentry))
257 return 0;
258
259 /* Check interest of this mark in case event was sent with two marks */
260 if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS))
261 return 0;
262
263 return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie);
264 }
265
fsnotify_handle_event(struct fsnotify_group * group,__u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * name,u32 cookie,struct fsnotify_iter_info * iter_info)266 static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask,
267 const void *data, int data_type,
268 struct inode *dir, const struct qstr *name,
269 u32 cookie, struct fsnotify_iter_info *iter_info)
270 {
271 struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
272 struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info);
273 int ret;
274
275 if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) ||
276 WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info)))
277 return 0;
278
279 if (parent_mark) {
280 /*
281 * parent_mark indicates that the parent inode is watching
282 * children and interested in this event, which is an event
283 * possible on child. But is *this mark* watching children and
284 * interested in this event?
285 */
286 if (parent_mark->mask & FS_EVENT_ON_CHILD) {
287 ret = fsnotify_handle_inode_event(group, parent_mark, mask,
288 data, data_type, dir, name, 0);
289 if (ret)
290 return ret;
291 }
292 if (!inode_mark)
293 return 0;
294 }
295
296 if (mask & FS_EVENT_ON_CHILD) {
297 /*
298 * Some events can be sent on both parent dir and child marks
299 * (e.g. FS_ATTRIB). If both parent dir and child are
300 * watching, report the event once to parent dir with name (if
301 * interested) and once to child without name (if interested).
302 * The child watcher is expecting an event without a file name
303 * and without the FS_EVENT_ON_CHILD flag.
304 */
305 mask &= ~FS_EVENT_ON_CHILD;
306 dir = NULL;
307 name = NULL;
308 }
309
310 return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type,
311 dir, name, cookie);
312 }
313
send_to_group(__u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * file_name,u32 cookie,struct fsnotify_iter_info * iter_info)314 static int send_to_group(__u32 mask, const void *data, int data_type,
315 struct inode *dir, const struct qstr *file_name,
316 u32 cookie, struct fsnotify_iter_info *iter_info)
317 {
318 struct fsnotify_group *group = NULL;
319 __u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
320 __u32 marks_mask = 0;
321 __u32 marks_ignored_mask = 0;
322 struct fsnotify_mark *mark;
323 int type;
324
325 if (WARN_ON(!iter_info->report_mask))
326 return 0;
327
328 /* clear ignored on inode modification */
329 if (mask & FS_MODIFY) {
330 fsnotify_foreach_obj_type(type) {
331 if (!fsnotify_iter_should_report_type(iter_info, type))
332 continue;
333 mark = iter_info->marks[type];
334 if (mark &&
335 !(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
336 mark->ignored_mask = 0;
337 }
338 }
339
340 fsnotify_foreach_obj_type(type) {
341 if (!fsnotify_iter_should_report_type(iter_info, type))
342 continue;
343 mark = iter_info->marks[type];
344 /* does the object mark tell us to do something? */
345 if (mark) {
346 group = mark->group;
347 marks_mask |= mark->mask;
348 marks_ignored_mask |= mark->ignored_mask;
349 }
350 }
351
352 pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignored_mask=%x data=%p data_type=%d dir=%p cookie=%d\n",
353 __func__, group, mask, marks_mask, marks_ignored_mask,
354 data, data_type, dir, cookie);
355
356 if (!(test_mask & marks_mask & ~marks_ignored_mask))
357 return 0;
358
359 if (group->ops->handle_event) {
360 return group->ops->handle_event(group, mask, data, data_type, dir,
361 file_name, cookie, iter_info);
362 }
363
364 return fsnotify_handle_event(group, mask, data, data_type, dir,
365 file_name, cookie, iter_info);
366 }
367
fsnotify_first_mark(struct fsnotify_mark_connector ** connp)368 static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
369 {
370 struct fsnotify_mark_connector *conn;
371 struct hlist_node *node = NULL;
372
373 conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
374 if (conn)
375 node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);
376
377 return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
378 }
379
fsnotify_next_mark(struct fsnotify_mark * mark)380 static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
381 {
382 struct hlist_node *node = NULL;
383
384 if (mark)
385 node = srcu_dereference(mark->obj_list.next,
386 &fsnotify_mark_srcu);
387
388 return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
389 }
390
391 /*
392 * iter_info is a multi head priority queue of marks.
393 * Pick a subset of marks from queue heads, all with the
394 * same group and set the report_mask for selected subset.
395 * Returns the report_mask of the selected subset.
396 */
fsnotify_iter_select_report_types(struct fsnotify_iter_info * iter_info)397 static unsigned int fsnotify_iter_select_report_types(
398 struct fsnotify_iter_info *iter_info)
399 {
400 struct fsnotify_group *max_prio_group = NULL;
401 struct fsnotify_mark *mark;
402 int type;
403
404 /* Choose max prio group among groups of all queue heads */
405 fsnotify_foreach_obj_type(type) {
406 mark = iter_info->marks[type];
407 if (mark &&
408 fsnotify_compare_groups(max_prio_group, mark->group) > 0)
409 max_prio_group = mark->group;
410 }
411
412 if (!max_prio_group)
413 return 0;
414
415 /* Set the report mask for marks from same group as max prio group */
416 iter_info->report_mask = 0;
417 fsnotify_foreach_obj_type(type) {
418 mark = iter_info->marks[type];
419 if (mark &&
420 fsnotify_compare_groups(max_prio_group, mark->group) == 0)
421 fsnotify_iter_set_report_type(iter_info, type);
422 }
423
424 return iter_info->report_mask;
425 }
426
427 /*
428 * Pop from iter_info multi head queue, the marks that were iterated in the
429 * current iteration step.
430 */
fsnotify_iter_next(struct fsnotify_iter_info * iter_info)431 static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
432 {
433 int type;
434
435 fsnotify_foreach_obj_type(type) {
436 if (fsnotify_iter_should_report_type(iter_info, type))
437 iter_info->marks[type] =
438 fsnotify_next_mark(iter_info->marks[type]);
439 }
440 }
441
442 /*
443 * fsnotify - This is the main call to fsnotify.
444 *
445 * The VFS calls into hook specific functions in linux/fsnotify.h.
446 * Those functions then in turn call here. Here will call out to all of the
447 * registered fsnotify_group. Those groups can then use the notification event
448 * in whatever means they feel necessary.
449 *
450 * @mask: event type and flags
451 * @data: object that event happened on
452 * @data_type: type of object for fanotify_data_XXX() accessors
453 * @dir: optional directory associated with event -
454 * if @file_name is not NULL, this is the directory that
455 * @file_name is relative to
456 * @file_name: optional file name associated with event
457 * @inode: optional inode associated with event -
458 * either @dir or @inode must be non-NULL.
459 * if both are non-NULL event may be reported to both.
460 * @cookie: inotify rename cookie
461 */
fsnotify(__u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * file_name,struct inode * inode,u32 cookie)462 int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
463 const struct qstr *file_name, struct inode *inode, u32 cookie)
464 {
465 const struct path *path = fsnotify_data_path(data, data_type);
466 struct fsnotify_iter_info iter_info = {};
467 struct super_block *sb;
468 struct mount *mnt = NULL;
469 struct inode *parent = NULL;
470 int ret = 0;
471 __u32 test_mask, marks_mask;
472
473 if (path)
474 mnt = real_mount(path->mnt);
475
476 if (!inode) {
477 /* Dirent event - report on TYPE_INODE to dir */
478 inode = dir;
479 } else if (mask & FS_EVENT_ON_CHILD) {
480 /*
481 * Event on child - report on TYPE_PARENT to dir if it is
482 * watching children and on TYPE_INODE to child.
483 */
484 parent = dir;
485 }
486 sb = inode->i_sb;
487
488 /*
489 * Optimization: srcu_read_lock() has a memory barrier which can
490 * be expensive. It protects walking the *_fsnotify_marks lists.
491 * However, if we do not walk the lists, we do not have to do
492 * SRCU because we have no references to any objects and do not
493 * need SRCU to keep them "alive".
494 */
495 if (!sb->s_fsnotify_marks &&
496 (!mnt || !mnt->mnt_fsnotify_marks) &&
497 (!inode || !inode->i_fsnotify_marks) &&
498 (!parent || !parent->i_fsnotify_marks))
499 return 0;
500
501 marks_mask = sb->s_fsnotify_mask;
502 if (mnt)
503 marks_mask |= mnt->mnt_fsnotify_mask;
504 if (inode)
505 marks_mask |= inode->i_fsnotify_mask;
506 if (parent)
507 marks_mask |= parent->i_fsnotify_mask;
508
509
510 /*
511 * if this is a modify event we may need to clear the ignored masks
512 * otherwise return if none of the marks care about this type of event.
513 */
514 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
515 if (!(mask & FS_MODIFY) && !(test_mask & marks_mask))
516 return 0;
517
518 iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
519
520 iter_info.marks[FSNOTIFY_OBJ_TYPE_SB] =
521 fsnotify_first_mark(&sb->s_fsnotify_marks);
522 if (mnt) {
523 iter_info.marks[FSNOTIFY_OBJ_TYPE_VFSMOUNT] =
524 fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
525 }
526 if (inode) {
527 iter_info.marks[FSNOTIFY_OBJ_TYPE_INODE] =
528 fsnotify_first_mark(&inode->i_fsnotify_marks);
529 }
530 if (parent) {
531 iter_info.marks[FSNOTIFY_OBJ_TYPE_PARENT] =
532 fsnotify_first_mark(&parent->i_fsnotify_marks);
533 }
534
535 /*
536 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
537 * ignore masks are properly reflected for mount/sb mark notifications.
538 * That's why this traversal is so complicated...
539 */
540 while (fsnotify_iter_select_report_types(&iter_info)) {
541 ret = send_to_group(mask, data, data_type, dir, file_name,
542 cookie, &iter_info);
543
544 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
545 goto out;
546
547 fsnotify_iter_next(&iter_info);
548 }
549 ret = 0;
550 out:
551 srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);
552
553 return ret;
554 }
555 EXPORT_SYMBOL_GPL(fsnotify);
556
fsnotify_init(void)557 static __init int fsnotify_init(void)
558 {
559 int ret;
560
561 BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);
562
563 ret = init_srcu_struct(&fsnotify_mark_srcu);
564 if (ret)
565 panic("initializing fsnotify_mark_srcu");
566
567 fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
568 SLAB_PANIC);
569
570 return 0;
571 }
572 core_initcall(fsnotify_init);
573